(Technical Field)
The present invention relates to a power conversion control apparatus incorporated in a power conversion system for converting a direct current (DC) voltage output from a converter into an alternating current (AC) using an inverter.
(Related Art)
Conventionally, techniques are known for variably controlling a switching speed for a plurality of semiconductor switching elements forming an inverter. In general, a lower switching speed can more reduce a surge voltage associated with switching operations, thereby prevent breakdown of the switching elements. However, loss reduction in the witching elements requires a higher switching speed. Therefore, it is required to change the switching speed properly depending on the situations.
An inverter apparatus disclosed in Japanese Patent No. 3052792 is configured to change the switching speed for the switching elements when a voltage of a DC power source applied to a gate drive circuit has reached a given threshold.
A power converter apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2014-11817 is configured such that a gate control circuit (an electronic control unit (ECU)) changes the switching speed for the switching elements based on an input voltage.
The inverter apparatus disclosed in Japanese Patent No. 3052792 is not configured such that a controller (being a control ECU) commands a switching speed change to the gate drive circuit. Therefore, the controller is unable to obtain any information about the switching speed.
A power converter disclosed in Japanese Patent Application Laid-Open Publication No. 2014-11817 is configured such that the gate control circuit changes the switching (SW) speed. The power converter apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2014-11817 is only configured to, based on results of the input voltage, change the SW speed. That is, it is not mentioned at what timing the switching speed is to be changed in response to the input voltage change command.
If the switching speed is changed without taking into account switching speed change timing, a high input voltage and high switching speed situation is likely to occur due to a reaction delay of the speed changing circuit, which may cause breakdown of the switching elements.
In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing a power conversion control apparatus capable of properly changing a switching speed for switching elements to meet breakdown prevention and loss reduction needs.